Composite abrasive attachment article for concrete power trowel machine

ABSTRACT

The invention provides a float trowel blade attachment for cement floor finishers comprising a rectangular section of sheet metal having a top surface and a bottom surface and having its edges optionally bent upwardly, means for providing to the top surface a three-sided rearwardly open pocket on the back of the section adjacent the leading edge thereof adapted to partially receive a finish trowel blade of the finisher, a spring clip secured to the top surface or the pocket-forming means and extending rearwardly therefrom so as to be engageable with the finish trowel blade to retain the section thereon, and wherein said rectangular sheet metal has attached to its bottom surface using an adhesive or mechanical attachment material interlayer, a composite rigid abrasive element bonded to a resilient backing.

This application claims the priority benefit under 35 U.S.C. section 119 of U.S. Provisional Patent Application No. 62/615,453 entitled “Composite Abrasive Attachment Article For Concrete Power Trowel Machine” filed on Jan. 10, 2018; and which is in its entirety herein incorporated by reference.

FIELD OF THE INVENTION

The present invention relates, in general, to tools used to finish freshly laid concrete surfaces. The present invention also relates to finishing machines for concrete and particularly to blade attachments which allow poured and partially dried concrete to be properly finished with a smooth surface. More particularly, the present invention relates to attachments to pre-existing trowel machines which allow the trowel machines to be converted into grinding machines thereby allowing the trowel machine to grind hardened concrete to a smooth finish.

The invention further relates to a composite abrasive article useful for use in trowel machines. The inventive article is an attachment for a concrete power trowel machine, wherein the attachment fixes onto the existing power trowel blade, facilitating the use of the power trowel for grinding and polishing hard concrete surfaces to high aesthetic quality.

BACKGROUND OF THE INVENTION

Concrete is one of the most widely used construction materials. Because of its strength, durability, ease of manufacture, ease of installation, and relatively low cost, it is frequently the material of choice for floors, walls, and the like. However, there are many instances where it is desirable to have a floor or wall surface with a pleasing high gloss finish or shine. In such cases, concrete may be overlooked in favor of other more high cost materials such as marble, stone, terrazzo, etc. Color concrete flooring has become very popular replacing the flooring materials previously mentioned as well as low cost tile flooring applications.

In pouring wet concrete, several steps are required to insure a smooth concrete surface finish after the concrete has partially dried. When the concrete is still in semi-fluid form, it is initially screeded through the use of a screed board or long wooden plank. Screeding is required to bring the wet concrete surface to a roughly equal height. Once the concrete is initially set at this height, the surface of the concrete is then treated with a float. The floating operation is used to settle large stones, smooth out the surface of the wet concrete, and settle the larger stones below the surface. After the float operation is performed and the concrete has partially dried, the freshly poured concrete may be troweled in order to bring the surface to a smooth finish. Utilizing a trowel machine with a plurality of blades, the surface of the concrete which is in a partially dried condition is contacted by the rotating blades of the trowel machine and produces a smooth finish surface on the concrete which is free of bubbles and also allows for evaporation of water which may rise to the surface. However, troweling needs to be completed prior to the concrete becoming too hard. Once the freshly poured concrete has hardened, the troweling machine and its corresponding flat blades will not sufficiently smooth the concrete surface.

Color concrete floors have some drawbacks when preparing the surface that include: 1) trowel machines may burn or take the color out of the color concrete floor if used too long while trying to take out imperfections; and 2) color concrete floors must be left in an imperfect or rough finish to harden to avoid burning the floor or taking the color out of the color concrete flooring. There is a need for a device and a method for preparing the concrete surface after the concrete has hardened.

In the past power trowel machines with trowel blades as well as grinding machines with grinding blades have been attempted in numerous ways. U.S. Pat. No. 3,936,212 title “Ride-Type Surface-Working Machines” depicts an example of a riding troweling machine for finishing large areas of concrete flooring utilizing traditional trowel blades. U.S. Pat. No. 3,934,377 titled “Concrete Surface Grinder” is an example of rotary concrete surface grinding and smoothing devices having a segmental diamond chip impregnated, engine driven, and a rotating grinding head. Using these machines requires the additional expense of having both a grinder and a trowel machine for finishing concrete surfaces. U.S. Pat. No. 5,567,503 titled “Polishing Pad with Abrasive Particles in a Non-Porous Binder” discloses a polishing pad of ultra-hard abrasive particles such as diamond or cubic boron nitride for use with non-porous thermoplastic polymers in polishing very had stones such as granite. These pads are designed for very hard stone and do not work as well for concrete surfaces with numerous imperfections. U.S. Pat. No. 6,058,922 titled “Grinding Blade for Trowel Machine” converts the trowel machine to a grinding machine by sliding a device over the trowel blade with a grinding stone attached to the device. Yet, these attachments over the trowel blade are not as desirable as having the grinding surface attached directly to the power trowel machine.

There have also been various methods attempted to finish concrete floors. U.S. Pat. No. 6,155,907 reissued as RE38,364 E titled “Method for Hardening and Polishing Concrete Floors, Walls, and the Like” discloses a method of hardening and polishing a concrete surface by applying a hardening/densifying silicate compound, allowing the chemical to soak into the surface of the concrete, drying the surface, applying a polishing compound and mechanically polishing the concrete surface. This patent also discloses other methods that all include a step of applying silicate polishing compounds or applying a hardening/densifying silicate compounds or both. U.S. Pat. No. 6,475,067 titled “Dry Method of Concrete Floor Restoration” discloses a method for restoring a concrete surface by dry grinding a concrete surface using a grinding grit, extracting the dust generated, repeating the dry grinding and applying a sealer. This process uses rotating diamond grinding disks that remove existing floor coatings or smooth out ruts or pitted concrete floor slabs attached to grinding machines such as the HTC-800 available from HTC Sweden. However, this method uses additional grinding machines and applies sealer coats after grinding.

In pouring wet concrete, several steps are required to insure a smooth concrete surface finish after the concrete has partially dried. When the concrete is still in semi-fluid form, it is initially screeded through the use of a screed board or long wooden plank. Screeding is required to bring the wet concrete surface to a roughly equal height. Once the concrete is initially set at this height, the surface of the concrete is then treated with a float. The floating operation is used to settle large stones, smooth out the surface of the wet concrete and settle the larger stones in the concrete below the surface. After the float operation is performed, the concrete has partially dried and the freshly poured concrete may be troweled in order to bring the surface to a smooth finish.

Utilizing a trowel machine with a plurality of blades, the surface of the concrete which is in a partially dried condition is contacted by the rotating blades of the machine and produces a smooth finish surface on the concrete which is free of bubbles and also allows for evaporation of water which may rise to the surface. However, troweling needs to be completed prior to the concrete becoming too hard. Once the freshly poured concrete has hardened, the troweling machine and its corresponding flat blades will not sufficiently smooth the concrete surface. If the freshly poured concrete has hardened to such an extent that the trowel blade or troweling machine will not properly work the concrete surface, a grinding stone is utilized to adequately smooth the concrete. A completely separate machine is utilized for grinding the surface and these machines contact the surface of the poured concrete with a grinding stone. A grinding machine operates to automatically smooth the surface with these rough grinding stones and the machine design has historically been different from the troweling machine due to the moving characteristics of the grinding stone and the like. As a result, the concrete finisher must have both a troweling machine and a grinding machine nearby in case the concrete hardens to such an extent that the trowel machine will not adequately smooth the surface of the poured concrete. It is therefore desirable for the concrete finisher to have on hand an apparatus allowing the conversion of a troweling machine to a grinding machine so that the overhead of having the two aforementioned machines is not necessary.

The traditional floor finishing process for providing a smooth dense floor typically associated with interior cast-in-place concrete, terrazzo, epoxy or co-polymer flooring involves using hand or mechanical power troweling. Power troweling machines are available in two basic styles: walk-behind and ride-on. These machines have, historically, been fitted with various types of steel blades or, more recently, plastic blades, for different aspects of the finishing process.

Most walk-behind power trowels include a single set of horizontal rotating blades encircled by a guard ring cage, a gas or electric engine and a handle for machine control and steering. The blades are attached to radially extending, spaced apart arms of a spider assembly or rotor, which is caused to rotate by a shaft driven by the engine. Each rotor typically mounts three- or four-blades and has a diameter ranging from 2 to 5 feet, giving a finished area per revolution of slightly more than 3 to almost 20 square feet. A typical 36-inch diameter walk-behind power trowel can finish 7000 to 15,000 square feet of concrete per day. Since walk-behind power trowels weigh less than ride-on trowels, they can be put on slabs sooner than their heavier counterparts. Even so, concrete needs to be a bit harder before power troweling than hand troweling.

Configured with either two or three sets of rotating blades, typical ride-on power trowels range in size from approximately 6 feet to slightly more than 10 feet in path width, to produce a troweled area of about 17 to 40 square feet, respectively. The largest units weigh more than a ton and can finish about 30,000 square feet per day. Ride-on trowels can be configured with two or more rotors, each having a plurality of radially oriented, spaced-apart blades. The blades on adjacent rotors may be overlapping or non-overlapping. Overlapping blades are spaced so that each set of blades overlaps slightly with the other set as the blades rotate. Because the two sets overlap, no unfinished concrete is left between them, as is the case with a non-overlapping configuration.

There are three basic types of blades for both walk-behind and ride-on trowels: float, finish and combination. Float blades are normally about ten inches wide and are intended to run flat on the concrete shortly after the concrete has been poured and screeded. The blades, which have their leading edges turned up slightly so that fresh concrete won't be damaged, push aggregate down into the concrete and bring water to the surface. Finishing blades are used after floating is completed. They, typically, are rectangular in shape with the opposite long sides serving as the finishing edges. About six inches wide, they are pitched during use to apply more pressure to the concrete than with float blades, so that the surface can be compacted. The pitch angles for finishing blades are increased slightly on each successive pass to put increasingly greater pressure on the concrete surface. If the blades are pitched too much, a washboard effect may result, necessitating reducing the blades' pitch and refinishing the surface. Combination blades can both float and finish. They are, typically, about 8 inches wide, and are a combination of floating and finishing blades. They have a finishing edge and a float edge, are normally wider than finishing blades but narrower than float blades, and are more expensive than either finishing or floating blades. Combination blades are popular because operators don't have to stop and change the blades on each rotor for each operation. Their disadvantage is that they are not as efficient at either floating or finishing as the blades designed specifically for these jobs. One edge of the combination blade is pitched upwardly for floating, the pitched edge allowing fresh concrete to flow under the blade during floating, and the opposite edge is flat for finishing.

Mounting systems for mounting the blades, whether float, finish or combination, to the trowel arms on the rotors vary. In many systems, blades are bolted directly to the trowel arm. In other systems, the blades are connected to a mounting bar and the bar is bolted to the trowel arm.

During the final stage of finishing, a finish or combination blade is used to provide a smooth, dense finish. During this stage, burnish marks can occur on the finish, which are generally caused by the steel from which these blades have historically been made. In the past, to avoid these burnish marks, power troweling would have to stop and hand finishing would have to be used to complete the finishing process, which is both time and labor intensive. One relatively recent solution to the burnishing problem has been substituting plastic for steel as the material for the finishing blades. However, in most instances, the plastic blades are not strong or rigid enough to finish the concrete floor to an optimum level. Moreover, plastic blades can only be used on walk-behind trowels, as the ride-on trowels are much too heavy for the plastic blades.

Accordingly, there still exists a need for a stronger, more rigid blade that can be used on both styles of power trowels while also providing a burnish-free finish for many different types of floor systems.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a bottom view of a conventional motorized rotational troweling machine with the composite abrasive article of the invention attached to the trowel blades.

FIG. 2 illustrates the composite abrasive article having the rigid abrasive elements.

FIG. 2A is a photo showing the composite abrasive article having the rigid abrasive elements.

FIG. 3 shows the composite abrasive article comprises rigid abrasive elements of FIG. 2 bonded to a resilient backing.

FIG. 3A illustrates a photo showing the composite abrasive article comprising rigid abrasive elements of FIG. 2 bonded to a resilient backing.

FIG. 4 shows the back of a float trowel metal blade with mechanical attachment interlayer. FIG. 4A is photo of a prototype metal plate with a mechanical attachment interlayer.

FIGS. 5 and 5A is a perspective view of one of the float trowels embodying the present invention in a position wherein it is about to be mounted/applied to one of the finish trowel blades of the cement floor finisher.

FIG. 6 shows the adhesive backing or mechanical (velcro) backing that is attached to the float trowel as well as the resilient backing having abrasive particles that are part of the invention.

FIG. 6A illustrates the novel product of the invention wherein the floating blade has incorporated therein the adhesive layer and composite abrasive element.

FIG. 7 illustrates the composite abrasive attachment assembly mounted on trowel blade.

FIG. 8 shows the composite abrasive attachment articles installed on a trowel machine.

FIG. 9 is a prototype photo of the embodiment of FIG. 8.

FIG. 10 is an alternate embodiment to the one of FIG. 3 showing a two layer substrate having openings for placing circular abrasive elements.

FIG. 11 shows the two layer substrate including the abrasive element placed in the opening of the substrate.

SUMMARY OF THE INVENTION

The instant invention provides a composite abrasive article having rigid abrasive elements bonded to a resilient backing. The rigid abrasive elements are further attached to a metal plate using an adhesive or mechanical attachment material interlayer. Suitable metal plates are described in the concrete finishing industry as “float” blades.

The composite abrasive attachment assembly includes mechanical mounting features to attach the composite abrasive assembly onto an existing concrete power trowel blade.

One or more composite abrasive attachment articles may be installed and removed from each of the trowel machine blades without requiring disassembly of the power trowel blades from the machine trowel head.

The composite abrasive attachment article may be utilized with hand-held, walk-behind, or ride-on power trowel machines.

The invention also provides a float trowel blade attachment for cement floor finishers comprising a rectangular section of sheet metal having a top surface and a bottom surface and having its edges optionally bent upwardly, means for providing to the top surface a three-sided rearwardly open pocket on the back of the section adjacent the leading edge thereof adapted to partially receive a finish trowel blade of the finisher, a spring clip secured to the top surface or the pocket-forming means and extending rearwardly therefrom so as to be engageable with the finish trowel blade to retain the section thereon, and wherein said rectangular sheet metal has attached to its bottom surface using an adhesive or mechanical attachment material interlayer, a composite rigid abrasive element bonded to a resilient backing.

The invention further provides in combination with a cement floor finisher having one or more finishing trowel blades mounted for rotation thereon and adapted to be moved over a floor to be finished, corresponding float trowels underlying the finish trowel blades, said float trowels having rearwardly open pockets formed thereon adjacent the leading edges thereof partially receiving the finish trowel blades, means on the float trowels for releasably retaining the float trowels on the finish trowel blades, wherein said float trowel includes attached to its bottom surface using an adhesive or mechanical attachment material interlayer, a composite rigid abrasive element having a resilient backing bonded to said bottom surface.

The invention also provides a float trowel for cement floor finishers comprising a rectangular section of sheet metal having a top surface and a bottom surface and optionally having its leading edge and its side edges bent upwardly, means providing upright surfaces on the upper side of said section arranged to engage the leading edge and end edges of a finish trowel of a cement floor finisher so that said section can be held against lateral displacement with respect to the finish trowel by said surfaces, a rearwardly extending spring clip secured to said section extending rearwardly over the upper surface of said section so as to be engageable with the finish trowel to retain said section thereon and wherein said metal sheet has attached to its bottom surface using an adhesive or mechanical attachment material interlayer, a composite rigid abrasive element bonded to a resilient backing.

DETAILED DESCRIPTION OF THE INVENTION

The composite abrasive article comprises rigid abrasive elements bonded to a resilient backing. The rigid abrasive elements contain diamond or other suitable abrasive particles held together with resin, ceramic, metal, or combinations thereof. The abrasive particles may be of specific composition and size to facilitate grinding, honing, polishing, and burnishing of hard concrete surfaces. The resilient backing may be woven cloth, foam, felt, nonwoven material, or combinations thereof. The rigid abrasive elements are further attached to a metal plate using an adhesive or mechanical attachment material interlayer to form a composite abrasive attachment assembly. Suitable metal plates are described in the concrete finishing industry as “float” blades.

The composite abrasive attachment assembly includes mechanical mounting features to attach the composite abrasive assembly onto an existing concrete power trowel blade. One or more composite abrasive attachment articles may be installed and removed from each of the trowel machine blades without requiring disassembly of the power trowel blades from the machine trowel head.

The composite abrasive attachment article may be utilized with hand-held, walk-behind, or ride-on power trowel machines.

Referring to FIG. 1, the attachment 1 of the invention fixes onto the existing power trowel blade 2, facilitating the use of the power trowel for grinding and polishing hard concrete surfaces to high aesthetic quality. The replaceable attachment 1 to a trowel blade 2 may be provided with a replaceable trailing edge. The replaceable attachment which is fixed into trowel blade 2 is then attachable to a conventional motorized gear rotor 3 by attachment shafts 4. This is a bottom view that blocks view of an engine that provides rotational power to the motorized gear rotor 3 in conventional practice. Typically, a handle shaft 5 with a handle 6 houses a control shaft that can be rotated by blade-control knob 7 to cause the blade 2 with attachment 1 to be either flat against a cement surface being troweled or for an upwardly-bent leading edge 8 to be raised. A circular guard 9 may be positioned at the outside diameter of rotation of the blades with attachment to prevent their contact with outside objects when the blades with attachments are being rotated. There are also conventional riding models of motorized rotary trowel blades that function similarly in relation to the rotational features and adjustment of the angle of the blade. This invention is related to the structure attached to the blade, not the rotary mechanism or adjustment of the angle of the blades in relation to the surface of cement being troweled.

The composite abrasive article 21 of the invention includes the rigid abrasive elements 10 as shown in FIG. 2 bonded to a resilient backing 11 as shown in FIG. 3 and FIG. 3A shown as a photo of a prototype.

The rigid abrasive elements 10 contain diamond or other suitable abrasive particles held together with resin, ceramic, metal, or combinations thereof. The abrasive particles of element 10 may be of specific composition and size to facilitate grinding, honing, polishing, and burnishing of hard concrete surfaces. The resilient backing 11 may be woven cloth, foam, felt, nonwoven material, or combinations thereof. The rigid abrasive elements 10 which are bonded to the resilient backing 11 are further attached to the bottom surface of a metal plate 28 (bottom of float blade) using an adhesive or mechanical attachment material interlayer 13 as illustrated in.

FIG. 4 and the prototype FIG. 4A shown as a photo. Suitable metal plates are described in the concrete finishing industry as “float” blades as shown in FIG. 5A and FIG. 5B.

As shown in FIG. 5, the finishing trowel blades may optionally have their outer and inner ends bent upwardly slightly, as indicated at 25 and 26, the side edges 27 and 28 are not so bent. This is particularly true of the trailing edge 27 which imparts the smooth finish surface to the floor as the trowels are moved thereover. The finish trowels also are usually relatively narrow, as illustrated in FIG. 5, and because of their size and the lack of the upturned side edges the finish trowels are unsuitable for performing the floating operation even though the trowels may be adjusted by a knob to assume perfectly horizontal positions.

The float trowel blade embodying the present invention as shown in FIG. 5A consists of a relatively broad section of sheet metal 28 which not only has its ends bent upwardly as indicated at 30 and 31 but also has the side edges bent upwardly as indicated at 32 and 33. It should be noted that the bents are optional. A cap 34 extends from end to end of the float trowel and may be spot welded thereto adjacent the leading edge 32. This cap extends from adjacent the leading edge toward the trailing edge 33 so as to substantially cover over the forward half of the finish trowel when the neat trowel is applied thereto. The ends of the cap may be bent downwardly, as indicated at 36, over the upwardly bent ends 30 and 31 or the finish trowel. In this manner the cap 34 cooperates with the body of the float trowel to form a rearwardly open pocket designed to receive approximately the forward half of the finish trowel. A spring clip 37 may be secured to the top of the cap such as by spot welding 38 and this spring clip is formed with a detent 39 adapted to bev snapped over the bar 17 on the finish trowel to retain the float trowel in position.

The construction of the entire attachment of the invention which includes the composite abrasive elements is fully illustrated in FIG. 6. Referring to FIG. 6, the attachment of the invention consists of three components: Component one is the device illustrated in FIG. 5A to which is attached on the bottom surface thereof the elements of FIG. 4 and FIG. 3 respectively. The device of FIG. 5A consists of a relatively broad section of sheet metal 28 having a top surface and a bottom surface optionally having its ends bent upwardly as indicated at 30 and 31 but also optionally has the side edges bent upwardly as indicated at 32 and 33. It should be noted that the bents are optional. A cap 34 extends from end to end of the float trowel and may be spot welded thereto adjacent the leading edge 32. This cap extends from adjacent the leading edge toward the trailing edge 33 so as to substantially cover over the forward half of the finish trowel when the neat trowel is applied thereto. The ends of the cap may be bent downwardly, as indicated at 36, over the upwardly bent ends 30 and 31 or the finish trowel. In this manner the cap 34 cooperates with the body of the float trowel to form a rearwardly open pocket designed to receive approximately the forward half of the finish trowel. A spring clip 37 may be secured to the top of the cap such as by spot welding 38 and this spring clip is formed with a detent 39 adapted to be snapped over the bar 17 on the finish trowel to retain the float trowel in position.

Component two is the adhesive component or mechanical attachment material interlayer 13 (such as hook and loop or VELCRO™) which is attached to bottom surface 28 of the metal.

Component three as shown in FIG. 6 is the abrasive element 21 which has abrasive elements 10 bonded to a resilient backing 11. Component three is bonded to component two which component includes the adhesive component or mechanical attachment means.

FIG. 6A illustrates the novel product of the invention wherein the floating blade 46 has incorporated therein the adhesive layer 13 and composite abrasive element 21.

FIG. 7 shows the the composite abrasive attachment assembly 21 mounted on a trowel blade. The composite abrasive attachment assembly includes mechanical mounting features to attach the composite abrasive assembly onto an existing concrete power trowel blade

FIG. 8 is a bottom view of a trowel machine showing the abrasive attachment of the invention 21 having abrasive elements 10 bonded to a resilient backing 11 mounted on the blades of the trowell machine. One or more composite abrasive attachment articles may be installed and removed from each of the trowel machine blades without requiring disassembly of the power trowel blades from the machine trowel head.

FIG. 9 is a photo of a prototype as shown in FIG. 8.

FIG. 10 illustrates a substrate 44 consisting of layers 40 and 41 and having openings 42 suitable for placing abrasive elements.

The substrate 44 is comprised of two or more non woven layers 40 and 41 laminated together with an adhesive interlayer. With typical single-layer non woven pads, holes are die-cut through the thickness of the pad to provide apertures for inserting secondary grinding and polishing elements. The composite nature of the laminated pad allows inclusion of certain features in the pad assembly, such as for example, blind-hole insert pockets. Such precisely-dimensioned features are not possible with a single-layer non woven pad construction. The composite pad construction further permits selection of component non woven materials for each layer having different, desirable properties. When combined in the assembled construction, each distinct layer contributes uniquely to enhance the performance of the pad assembly.

The component non woven layers may include fibers selected from, for example, polyester, nylon, polypropylene, rayon, acrylic, glass, and natural fibers. Nonwoven mat bonding materials may include, for example, latex, acrylic, and phenolic resins.

FIG. 11 illustrates a substrate 44 consisting of layers 40 and 41 and having including abrasive elements 43. The abrasive insert articles 43 are manufactured as follows: A mix of materials which include a curable resin (thermally curable or radiation curable), a silane coupling agent, a photoinitiator, a filler, thermal initiator, mineral fiber, inorganic powders and agglomerated abrasive particles are mixed together to form an abrasive slurry. The slurry components are mixed together, using an electric mixer and a four-blade impeller at 300 rpm for ˜15 minutes. or longer as required. A silicone mold is sprayed with a mold release agent and allowed to air-dry for ˜5 minutes at room temperature.

The abrasive slurry mix is then poured into the mold cavity. The mold is agitated by hand to release air bubbles from the mold surfaces and from within the slurry liquid. A nonwoven insert substrate produced as described above is placed in the mold cavity and downward pressure applied by hand to force the slurry into the lofty nonwoven face of the insert substrate.

A UVA light source is then placed on a horizontal surface with the UV bulb and reflector facing upward. The UV lamp is turned on and allowed to warm up for 15-30 minutes with the power switch set to “standby”.

The silicone mold containing the insert substrate and abrasive slurry is then placed directly onto the UV lamp shielding glass above the UV lamp bulb. The UV power source is switched on to “high.” After ˜15 seconds, the abrasive slurry which resides impregnated into the insert substrate is at least partially cured to a rigid state, and the mold is removed from over the UV lamp.

The at least partially cured abrasive insert is then removed from the silicone mold by peeling the elastomeric mold body from the insert. The de-molded, at least partially cured insert is then placed back on the UV light source for ˜40 seconds to ensure complete curing of the abrasive insert.

Useful abrasive particles may comprise, for example, fused aluminum oxide (including white fused alumina, heat-treated aluminum oxide, and brown aluminum oxide), ceramic aluminum oxide, heated treated aluminum oxide, silicon carbide, diamond (natural and synthetic), cubic boron nitride, boron carbide, titanium carbide, garnet, fused alumina-zirconia, ceramic alumina-zirconia, diamond, zirconia, and combinations thereof. Of these, diamonds are preferred. Useful diamonds may be either natural diamonds or man-made diamonds. The diamonds may include a surface coating (e.g., nickel or other metal) to improve the retention of the diamonds in the resin matrix.

Abrasive particles may also be present in abrasive agglomerates. Such agglomerates comprise a plurality of the abrasive particles, a matrix material, and optional additives. The matrix material may be organic and/or inorganic. The matrix material can be, for example, polymer resin, glass (e.g., vitreous-bond diamond aggregates), metal, glass-ceramic, ceramic (e.g., ceramic-bond agglomerates), or a combination thereof. For example, glass, such as silica glass, glass-ceramics, borosilicate glass, phenolic, epoxy, acrylic, and the other resins can be used as the agglomerate matrix material. Abrasive agglomerates may be randomly shaped or have a selected shape associated with them.

Fired agglomerated particles are manufactured according to our U.S. provisional application Ser. No. 62/427,811 filed Nov. 30, 2016 the entire contents of which are incorporated by reference herein.

The entire contents of my co-pending application U.S. Ser. No. 15/371,149 entitled “Composite Article For Maintaining And Cleaning Hard Surfaces” filed Dec. 6, 2016; is in its entirety herein incorporated by reference.

When float trowels constructed as above described are applied to the finish trowels on the machine, the machine may be operated in very much the conventional manner except that a knob is adjusted so that the finish trowels and consequently the float trowels thereon will assume perfectly horizontal positions which are required in performing the floating operation. As the float trowels have upwardly bent side edges, particularly the leading edge 32, there is no tendency of the float trowels to dig into the wet cement in performing the floating operation.

Furthermore, as the float trowels have their pockets open rearwardly and are applied over the leading edge 28 of the finish trowels, there is very little danger or tendency for the float trowels to become displaced from the finish trowels. In many instances the retaining spring clip 37 may be unnecessary due to the fact that the drag on the float trowels in the course of their movement tends to push the float trowels onto the finish trowels.

When the floating operation is completed the spring clips 37 may be sprung upwardly to release the float trowels and they may be easily and quickly removed. This exposes the bottom surfaces of the finish trowels and the machine may then be used in the manner to perform the finishing operation in the usual manner.

All patents, patent applications and publications cited in this application including all cited references in those patents, applications and publications, are hereby incorporated by reference in their entirety for all purposes to the same extent as if each individual patent, patent application or publication were so individually denoted.

While the many embodiments of the invention have been disclosed above and include presently preferred embodiments, many other embodiments and variations are possible within the scope of the present disclosure and in the appended claims that follow. Accordingly, the details of the preferred embodiments and examples provided are not to be construed as limiting.

It is to be understood that the terms used herein are merely descriptive rather than limiting and that various changes, numerous equivalents may be made without departing from the spirit or scope of the claimed invention. 

What is claimed is:
 1. A float trowel blade attachment for cement floor finishers comprising a rectangular section of sheet metal having a top surface and a bottom surface and having its edges optionally bent upwardly, means for providing to the top surface a three-sided rearwardly open pocket on the back of the section adjacent the leading edge thereof adapted to partially receive a finish trowel blade of the finisher, a spring clip secured to the top surface or the pocket-forming means and extending rearwardly therefrom so as to be engageable with the finish trowel blade to retain the section thereon, and wherein said rectangular sheet metal has attached to its bottom surface using an adhesive or mechanical attachment material interlayer, a composite rigid abrasive element bonded to a resilient backing.
 2. In combination with a cement floor finisher having one or more finishing trowel blades mounted for rotation thereon and adapted to be moved over a floor to be finished, corresponding float trowels underlying the finish trowel blades, said float trowels having rearwardly open pockets formed thereon adjacent the leading edges thereof partially receiving the finish trowel blades, means on the float trowels for releasably retaining the float trowels on the finish trowel blades, wherein said float trowel includes attached to its bottom surface using an adhesive or mechanical attachment material interlayer, a composite rigid abrasive element having a resilient backing bonded to said bottom surface.
 3. A float trowel for cement floor finishers comprising a rectangular section of sheet metal having a top surface and a bottom surface and optionally having its leading edge and its side edges bent upwardly, means providing upright surfaces on the upper side of said section arranged to engage the leading edge and end edges of a finish trowel of a cement floor finisher so that said section can be held against lateral displacement with respect to the finish trowel by said surfaces, a rearwardly extending spring clip secured to said section extending rearwardly over the upper surface of said section so as to be engageable with the finish trowel to retain said section thereon and wherein said metal sheet has attached to its bottom surface using an adhesive or mechanical attachment material interlayer, a composite rigid abrasive element bonded to a resilient backing.
 4. The float trowel blade attachment of claim 1, wherein said adhesive is a thermoset adhesive.
 5. The float trowel blade attachment of claim 1, wherein said mechanical attachment material interlayer uses a hook and loop means.
 6. The float trowel blade attachment of claim 1, wherein said abrasive element includes diamond particles as the abrasive.
 7. The float trowel blade attachment of claim 1, wherein said abrasive element includes cubic boron nitride.
 8. The float trowel blade attachment of claim 1, wherein said abrasive element includes boron carbide.
 9. The float trowel blade attachment of claim 1, wherein said abrasive element includes titanium carbide.
 10. The float trowel blade attachment of claim 1, wherein said abrasive element includes silicon carbide.
 11. The float trowel blade attachment of claim 1, wherein said abrasive element includes zirconia.
 12. The float trowel blade attachment of claim 1, wherein said abrasive element includes fused aluminum oxide.
 13. The float trowel blade attachment of claim 1, wherein said composite rigid abrasive element includes a substrate made of two or more non woven layers.
 14. The float trowel blade attachment of claim 13, wherein said non woven layers include polyester fibers.
 15. The float trowel blade attachment of claim 13, wherein said non woven layers include nylon fibers.
 16. The float trowel blade attachment of claim 13, wherein said non woven layers include polypropylene fibers.
 17. The float trowel blade attachment of claim 13, wherein said non woven layers include rayon fibers.
 18. The float trowel blade attachment of claim 13, wherein said non woven layers include acrylic fibers.
 19. The float trowel blade attachment of claim 13, wherein said non woven layers include glass fibers.
 20. The float trowel blade attachment of claim 13, wherein said non woven layers include mixtures of polyester and polypropylene fibers. 